Tuberous sclerosis (TS) is an autosomal dominant genetic disease that affects 1 in 10,000 children. It is characterized by benign growths (hamartomas/hamartias) that affect multiple organ systems, including the brain, heart, lungs, kidneys, and skin. The morbidity of TS is often profound. 75% of TS patients experience seizures, 40% are mentally retarded, and 40% have autism. These affected children place a great strain on their family's and society's resources. The molecular pathogenesis of TS is unknown. Approximately one half of TS families show evidence of linkage to DNA markers on chromosome 9q34, and a little less than half show evidence of linkage to chromosome 16p13 markers. We propose to identify the TS gene on 9q34 by positional cloning techniques, to correlate genotypic lesions with clinical features, and explore the molecular pathogenesis of the disease. Specifically, a high resolution map and contig of 9q34 will be constructed by pulsed field gel/Southern blot analysis, fluorescence in-situ hybridization, genetic linkage mapping, and use of a cosmid library and YACs from the region; the TS gene will be identified by a search for structural DNA alterations in affected patients and identification of appropriate candidate genes; mutational analysis in affected patients will be performed; a mouse model of the disease will be created by homologous recombination experiments in embryonal stem cells followed by germline passage in chimeric animals. Identification of the gene will have major importance for genetic counseling in TS, understanding the pathogenesis of the condition, and design of rational therapies. It is also likely that understanding the TS gene will have implications for understanding regulation of cell growth and neuro-development.